The Cyst is a common specimen in Killing Floor 2. It is classified as a lesser enemy, and therefore, cannon fodder. Cysts are generally considered to be the weakest specimens in the game, whose only purpose is to populate the level.
Cysts are slow moving and not very resilient, it's easy to underestimate cysts. They aren't a threat when you see them coming or when they are alone, but they don't come at you like that. They come in hordes,they come from the flanks, and they latch on to you so the more dangerous Zeds can catch you up and take a bite. Don't give them the chance.